Could you share a test file? It will help to save time to recreate your scenario. Then I can have a try on it.
For sharing file, you may upload it to OneDrive or any other cloud drive and then post the link here. *Please make sure you have removed any sensitive or private information in the sample file before uploading.
Based on your description, you want all the value to be changed when you change the currency.
In a separate sheet or a range of cells, list all the currencies and their conversion rates. Then it can be used in formula.